Engine/Transmission (1994 - 1998) Boost pressure

[MLee]

Where should my boost pressure be when towing, in 4th gear? At 50-55 mph

it is at 10 psi some times 12-15 not offten though. In third (Manual trans) with higher rpms it will go to 20# but will pull better when I drop the boost to12# by foot on a grade up hill. It has the stock fuel plate slide forward 1/16 from full forward, and cover back just a hair. I changed my fuel filter in April, and am thinking of doing it again to see if this will help. Truck seems to run fine.

Any suggestions?

Thanks

 

[ewcmr2]

Boost should have direct correlation to throttle position. More throttle equals more boost until the governor springs reduce fuel at higher rpm.

For my truck 5-15psi covers most normal cruise pressures. Downhill would equal zero, uphill 15+.

 

[Nyoest]

If by cover back a hair you mean your afc is moved to the rear of truck it will limit the fueling on low boost more than stock. You can slide it forward for more oomph.



The boost level is directly related to the right foot. The reason it pulls better at ten to twelve pounds of boost is more than likely the rpm your running at. Stock my twelve valve did best when towing about 2100 much more than that it was just more rpm and no power. A 4,000 gsk fixed that little problem and puts a smile on my face every time I tow now. I don't tow at crazy rpm but it is nice to run it up to 2600-2800 at full power and grab the next gear and be right back at the sweet spot of the torque curve when you get back on the throttle. Of course the load will dictate driving habits, mine are never under 12,000 it seems.

 

[Nyoest]

And to answer your original question about 20 #s boost is max. Your numbers are typical if your not an aggresive driver.

 

[Mhannink]

boost is related to engine load more then anything else. gearing, weight, aerodynamics, grade, wind speed and direction, rpm, and ground speed will all affect the boost. example empty cruising boost is say 3-5 psi. truck and trailer loaded say 15 to 18k gcw all other conditions the same at same cruise speed boost might be 8-10. the engine is working harder loaded and produces more heat which drives the turbo harder and produces more boost. ewmcr2 is right to a point but clear.



remember that boost pressure is a measurment of the restriction in the intake system. the turbo flows air the restrictions create pressure as you are trying to pushing more air through the intake then it can handle. rpm will affect this, but there are a lot of conditions that have to be taken into account. the gauage is nice for an indication of how hard the engine is working more boost increased load. pyro is also good they sort of work in conjunction with each other. as far as an awnser to your question i would say that it depends very much on the conditions all those stated above. watch your guages pretty close and take note on the conditions and get an idea of how your truck runs then you'll know if you have a problem occurring. does that help?

 

[surfbeetle]

For your exhaust temps (pyro), measured pre turbo, you want to be in the 1100-1300° range, max. As mentioned, a stock 12v is 20 psi boost, with a torque plate and a boost elbow, you can get up to 40 psi. The sweet spot for a 12v is going to be around 500° and 2000 rpms.

 

[MLee]

Thanks for all your input. I am going to check a few things out that are obvious offenders and see this helps. It just might be me, not enough vitamins.